Transseptal crossing system

ABSTRACT

A self-contained, battery powered transseptal crossing system is disclosed. An elongate, flexible electrically conductive needle body has a proximal end and a distal end. An insulation layer surrounds the sidewall and leaves exposed a distal electrode tip. A generator is configured to deliver RF energy to the electrode tip, and includes a processor configured to take impedance measurements at the tip to confirm contact with the intra atrial septum and/or confirm entry into the left atrium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit under 35 U.S.C. § 119(e) ofU.S. Provisional Application No. 63/070,167, filed Aug. 25, 2020 andU.S. Provisional Application No. 63/195,578, filed Jun. 1, 2021, theentireties of which are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

Transseptal crossing is used to access the left atrium crossing from theright atrium through the septal wall for any of a variety ofelectrophysiology (EP) or structural heart procedures. For example, theleft atrium may be accessed to assess hemodynamics and/or perform amitral valve repair or replacement procedure or mitral valvuloplasty, toaccommodate transvascular atrial fibrillation (AF) ablation procedures,or to implant left atrial occlusion devices among other procedures.

Crossing the septum normally requires locating and puncturing the fossaovalis to access the left atrium. Locating the fossa ovalis may beaccomplished using fluoroscopy and ultrasound, and potentiallyechocardiography.

Mechanical puncture through the tissue of the fossa ovalis can beaccomplished using a piercing tool such as a standard Brockenbroughneedle as is understood in the art. Alternatively, a transseptal needlehaving a radio frequency energized tip and pressure sensing or contrastinjection to confirm penetration may be used, such as those produced byBaylis Medical Company, Inc.

Notwithstanding the foregoing, there remains a need for an improvedtransseptal crossing needle and associated sheath and dilator system.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the presentinvention, a transseptal crossing system. The system includes atransseptal crossing needle comprising an elongate, flexible tubularbody, having a proximal end, a distal end and an electrically conductivesidewall defining a central lumen. An insulation layer surrounds thesidewall, leaving exposed a distal electrode tip. An end apertureextends distally from the central lumen through the distal electrodetip. A battery powered RF generator is configured to deliver RF energyto the electrode tip and also to measure impedance at the tip to provideinformation about the location of the electrode tip.

At least one side port may be provided through the tubular body, spacedproximally of the electrode tip. The needle may further comprise atleast one side electrode on the tubular body spaced proximally of theelectrode tip. The side electrode may be in the form of an annular ring.

The tubular body may have a step down in outside diameter, and may havea maximum outside diameter of about 0.035 inches. The distal electrodemay comprise a smooth, hemispherical surface. The sidewall may comprisea stainless steel tube.

The tubular body may have sufficient structural integrity to guide alarge bore catheter transvascularly through a septal wall and into aleft atrium of the heart, and may have sufficient structural integrityto guide a large bore catheter transvascularly through a septal wall andinto a left atrial appendage of the heart

There is also provided a method of providing access to the left atrium,comprising the steps of transvascularly advancing a transseptal needleinto the right atrium and into contact with the fossa; taking a firstimpedance measurement at the fossa; transmitting RF energy from abattery powered generator through the needle and to the fossa topenetrate the fossa and enter the left atrium; and taking a secondimpedance measurement to confirm location of the needle in the leftatrium.

The transvascularly advancing step may comprise advancing an assembly ofthe needle, a dilator and a sheath. The method may further comprise thestep of taking at least a third impedance measurement with an electrodeon the sheath.

There is provided in accordance with another aspect of the presentinvention a depth sensing dilator system for dilating a penetration in atissue plane. The system comprises an elongate flexible body, having aproximal end and a distal end; a tapered dilator segment on the body; atleast a first and second electrode spaced axially apart on the body; aprocessor; and an output.

The processor may be configured to send a first signal to the outputwhen the first electrode reaches a predetermined relationship with thetissue plane, and to send a second signal to the output when the secondelectrode reaches the predetermined relationship with the tissue plane.

The predetermined relationship may be when the electrode first contactsthe tissue plane, or when the electrode passes through the tissue planesuch as into a blood pool beyond the tissue plane. The output maycomprise at least one of an audio output, a visual output, or a tactileoutput.

The at least one electrode may be on the tapered dilator segment. Thefirst and second electrodes may be spaced axially apart on the tapereddilator segment. The dilator system may further comprise a thirdelectrode on the distal end. The first, second and third electrodes maybe approximately equally axially spaced apart.

The depth sensing dilator system may further comprise an RF generatorconfigured to deliver RF energy to at least one of the first and secondelectrodes. The system may be configured to determine impedance at atleast one of the electrodes. The RF generator may be battery powered.

There is also provided a method of sensing the depth of penetration ofan intravascular device through a tissue plane. The method comprises thesteps of providing an intravascular device having an elongate flexiblebody, having a proximal end and a distal end and at least a first andsecond electrode spaced axially apart on the body; advancing the bodythrough the tissue plane; generating a first output when the firstelectrode first contacts or penetrates through the tissue plane; andgenerating a second output when the second electrode first contacts orpenetrates through the tissue plane.

The tissue plane may be the atrial septum. The intravascular device maybe a dilator, having a tapered distal dilator segment. The dilator maycomprises at least three electrodes spaced axially apart along thedilator segment.

There is provided in accordance with another aspect of the presentinvention a transseptal crossing needle. The needle comprises anelongate, flexible tubular body, having a proximal end, a distal end andan electrically conductive sidewall defining a central lumen. A radiallyinwardly extending annular recess is provided at the distal end of thetubular body. The tubular body may have a first outside diameterproximally of the annular recess and the annular recess may have asecond, smaller outside diameter.

An electrode tip may have a proximally extending annular flange residingwithin the annular recess on the tubular body, and the electrode tip mayhave a third outside diameter distally of the annular flange and greaterthan the first diameter. An insulation layer may surround the sidewalland the annular flange, the insulation layer having an outside diameteracross the junction of the annular flange and tubular body ofapproximately the same as the third diameter.

The needle may additionally comprise an end aperture extending distallyfrom the central lumen through the distal electrode tip. The needle mayfurther comprise at least one side port through the tubular body spacedproximally of the electrode tip.

The transseptal crossing needle may further comprise at least one sideelectrode on the tubular body spaced proximally of the electrode tip;the tubular body may comprise a step down in outside diameter; and thedistal electrode tip may comprise a smooth, hemispherical electrodesurface.

The electrode tip may comprise a different material than the tubularbody. The electrode tip may comprises gold, and the tubular body maycomprise stainless steel. The outside diameter of the annular flange maybe spaced radially inwardly from the maximum outside diameter of theelectrode tip by at least about 0.002 inches. The wall thickness of theannular flange may be within the range of from about 0.002 inches toabout 0.005 inches.

Further features and advantages of the present invention will becomeapparent to those of skill in the art in view of the detaileddescription which follows, considered along with the associated drawingsand claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A schematically illustrates a transseptal crossing needle inaccordance with the present invention.

FIG. 1B is a detail perspective view of a distal end of the needle ofFIG. 1A.

FIG. 2A is a cannulated version of the transseptal crossing needle as inFIG. 1A.

FIG. 2B is a cross section taken along the line A-A in FIG. 2A.

FIG. 2C is a cross section taken along the line B-B in FIG. 2A.

FIG. 2D is a longitudinal cross section taken along the line C-C in FIG.2A.

FIG. 3 is a longitudinal cross section through the needle of FIG. 2A.

FIG. 4A-4B are detail views of the distal energy delivery tip of oneimplementation of the invention.

FIG. 5A-5B are detail views of the distal energy delivery tip of anotherimplementation of the invention.

FIG. 6A-6C are detail views of the distal energy delivery tip of anotherimplementation of the invention.

FIG. 7A-7C are detail views of the distal energy delivery tip of anotherimplementation of the invention.

FIG. 8A-8C are detail views of the distal energy delivery tip of anotherimplementation of the invention.

FIG. 9A-9B are detail views of the distal energy delivery tip of anotherimplementation of the invention.

FIG. 10A-10B are detail views of the distal energy delivery tip ofanother implementation of the invention.

FIG. 11 is a schematic cross section of a portion of a human heart,having a transseptal crossing system of the present invention positionedin the right atrium.

FIG. 12 is a view as in FIG. 11 , showing positioning of the distal tipof the transseptal crossing system at the fossa ovalis.

FIG. 13 shows penetration of the guidewire and cannula through the fossaovalis.

FIG. 14A is a schematic view of an assembled trans septal crossingsystem, having an RF needle extending through a dilator which is in turnextending through an access sheath.

FIG. 14B is an enlarged view of a distal portion of FIG. 14A.

FIG. 14C is a longitudinal cross section through the distal portionshown in FIG. 14B.

FIG. 15A is a detail view of a tapered portion of the RF needle.

FIG. 15B is a detail view as in FIG. 15A of a stepped outside diameterneedle.

FIGS. 16A-16D show RF needles with pre-set curves.

FIGS. 17A-17B show dilators having multiple electrodes.

FIGS. 18A-18B show additional multiple electrode dilator configurations.

FIG. 19 is a schematic representation of a depth sensing dilator systemfor dilating a penetration in a tissue plane

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1A and 1B illustrate an embodiment of a tissue penetratingapparatus 10 in a transseptal crossing system. Apparatus 10 comprises anelongate, flexible needle body 12 having a distal end 14 and a proximalend 16. The needle body 12 is configured to be inserted within andadvanced along a lumen of a body of a patient, such as a patient'svasculature, and maneuverable therethrough to a desired locationproximate material, such as tissue, to be perforated. In oneimplementation, the needle body 12 is configured for femoral vein accessand transvascular navigation into the right atrium, across the fossaovalis and into the left atrium.

A distal zone 18 may be provided with a preset curve duringmanufacturing, typically by mechanically bending in the case of a metaltubular body, or exposing it to heat while it is fixed in a desiredshape for a polymeric extrusion. In an alternate embodiment, the shapeof distal region is additionally or alternatively modifiable by theoperator during use.

The distal zone 18 may include a transition 20 between a larger diameterproximal portion of needle body 12 and a smaller outer diameter advancesegment 22 that extends between the transition 20 and the distal end 14.The transition 20 may provide tactical feedback once the advance segment22 has advanced through the perforation. In some embodiments, the outerdiameter of distal advance segment 22 may be no larger than about 0.8 mmto about 1.0 mm. For example, the outer diameter of advance segment 22may be about 0.9 mm (about 0.035″). The outer diameter of needle body 12proximal to the transition 20 may be no larger than about 0.040″ toabout 0.060″. For example, the outer diameter of needle body 12 may beabout 0.050″ (1.282 mm).

The distal end 14 terminates in a conductive electrode tip 24,variations of which are discussed below. The electrode tip 24 enablesdelivery of RF energy for piercing tissue, and optionally enables use asan ECG measuring device and/or an impedance measuring device. Theelectrode tip 24 and optionally the entire needle body 12 and advancesegment 22 may comprise a conductive and optionally radiopaque material,such as stainless steel, tungsten, platinum, or another electricallyconductive metal. If the needle body is not radiopaque, one or moreradiopaque markers may be affixed to needle body 12 such as to highlightthe location of the transition 20 or other important landmarks onapparatus 10.

The needle body 12 may comprise a hypotube, having a central lumenextending axially throughout its length. The advance segment 22 may be asmaller diameter hypotube, and may be provided with one or two or threeor more ports such as an end port through the electrode tip 24 and/orone or two or more side ports spaced axially apart along the side wall.Alternatively, the advance segment 22 may be a solid rod which may beslip fit concentrically within the lumen of a cannulated (tubular)needle body 12. Any conductive sections of the needle body 12 or advancesegment 22 are preferably provided with a continuous outer polymerjacket to provide electrical insulation of the entire device exceptwhere exposure is desired for functioning as an electrode such as theelectrode tip 24.

In the illustrated embodiment, proximal end 16 is carried by a hub 26,to which may be attached an electrical connector cable 28 and connector30. Tubing, adapters or other components may be attached to hub 26 aswell, depending upon the desired functionality. A proximal region of theneedle body may also have one or more depth markings to indicatedistances from distal tip 24, or other important landmarks. Hub 26 maycomprise a curve direction or rotational orientation indicator 32 thatis located on the same or opposite side of the apparatus 10 as theconcave side of the curve 18 in order to indicate the direction of curve18. Orientation indicator 32 may comprise an ink marking, etching,projection, or other feature that enhance visualization or tactilesensation.

Connector cable 28 may connect to an optional Electro-cardiogram (ECG)interface unit via connector 30. An optional ECG connector cableconnects an ECG interface unit to an ECG recorder, which displays andcaptures ECG signals as a function of time. A generator connector cablemay connect the ECG interface unit to an energy source such as agenerator (not illustrated). In this embodiment, the ECG interface unitcan function as a splitter, permitting connection of the electrosurgicaltissue piercing apparatus 102 to both an ECG recorder and generatorsimultaneously. ECG signals can be continuously monitored and recordedand the filtering circuit within the ECG interface unit and may permitenergy, for example RF energy, to be delivered from the generatorthrough electrosurgical apparatus 10 without compromising the ECGrecorder.

The generator may additionally be configured to detect impedance at theelectrode 24 and/or one or more electrodes along the sidewall of thedilator, needle body 12 or advance segment 22, as is discussed inadditional detail below.

In another, steerable embodiment (not shown) of apparatus 10, there maybe a deflection control on the hub 26 for operating a deflectionmechanism associated with the distal zone 18 and/or advance segment 22.One or two or more pull wires may extend from the proximal control tothe distal deflection mechanism to actively deflect the distal end inresponse to manipulation of the control as will be understood in theart. The control mechanism may be used to steer or otherwise laterallydeflect at least a portion of distal zone 18 or distal tip.

A generator may be a radiofrequency (RF) electrical generator that isdesigned to work in a high impedance range. Because of the small size ofenergy delivery tip 24 the impedance encountered during RF energyapplication is very high. General electrosurgical generators aretypically not designed to deliver energy in these impedance ranges, soonly RF generators having certain characteristics can be used with thisdevice.

In one embodiment, the energy is delivered as a continuous wave at afrequency between about 400 kHz and about 550 kHz, such as about 460kHz, a voltage of between 100 to 200 V RMS and a duration of up to 99seconds. A grounding pad 130 is coupled to generator 128 for attachingto a patient to provide a return path for the RF energy when generator128 is operated in a monopolar mode.

Other embodiments could use pulsed or non-continuous RF energy. Someembodiments for pulsed radio frequency energy have radio frequencyenergy of not more than about 60 watts, a voltage from about 200 Vrms toabout 400 Vrms and a duty cycle of about 5% to about 50% at about fromslightly more than 0 Hz to about 10 Hz. More specific embodimentsinclude radio frequency energy of not more than about 60 watts, avoltage from about 240 Vrms to about 300 Vrms and a duty cycle of 5% to40% at 1 Hz, with possibly, the pulsed radio frequency energy beingdelivered for a maximum of 10 seconds.

In one example, the generator can be set to provide pulsed radiofrequency energy of not more than about 50 watts, a voltage of about 270Vrms, and a duty cycle of about 10% at 1 Hz. Alternatively, the pulsedradio frequency energy could comprise radio frequency energy of not morethan about 50 watts, a voltage of about 270 Vrms, and a duty cycle ofabout 30% at 1 Hz.

In still other embodiments of apparatus 102, different energy sourcesmay be used, such as radiant (e.g. laser), ultrasound, thermal or otherfrequencies of electrical energy (e.g. microwave), with appropriateenergy sources, coupling devices and delivery devices depending upon thedesired clinical performance.

Details of exemplary RF needle and generator systems are describedbelow. The RF crossing needle may be a monopolar, conductive canula thatis insulated throughout the shaft with only a pre-defined surface areaand geometry at the tip exposed for contact on tissue. The electricalcircuit is completed through a grounding pad that is electricallyconnected to the patient's skin. The needle and grounding pad areconnected to a battery powered RF generator that delivers a preset,repeatable amount of energy during a discrete time window.

The distal tip of the RF may have a surface area within the range offrom about 0.25 mm² to about 2.5 mm² Geometry may be annular (e.g., inan implementation having a central aperture), blunt, spherical,typically non-planar.

In addition to the distal tip electrode, a second or third or moreelectrodes may be provided along the length of the needle or associateddilator. A series of electrodes spaced axially apart may be used such asfor depth monitoring and control, as is discussed further in connectionwith FIGS. 17A-18B, below. The RF generator may include a processorconfigured to associate a particular electrode in contact with the fossawith a depth of penetration of the needle through the fossa, and displayan indicium of that depth. With multiple electrodes, once the tip passesthrough the fossa, the impedance change is noted. Then as subsequentelectrodes are passed through the fossa, each time contact of anelectrode with the blood pool or the tissue changes, impedance changes.Each electrode may be in communication with the proximal hub and RFgenerator by way of a unique electrical conductor, such as a wire orconductive traces embedded between insulator layers in the sidewall.

One or two or five or more side electrodes may be placed within about0.25 mm to about 20 mm, in some embodiments from about 2 mm to about 10mm and in one example at least one electrode at about 5 mm from thedistal tip, for detecting depth of penetration. At least about two orfour or six or ten or more partial or full circumference band electrodescould be spaced uniformly (e.g., every 2-4 mm) along the length of thesidewall proximal to the distal tip. Helical pitch ring electrodes couldbe utilized if segmented electrodes are utilized. See FIGS. 17A-18B,discussed below.

Preferably the dilator design will accommodate protrusion of the needletip. Typically, the protrusion will be about 7-8 mm. This allows aseries of electrodes on the needle to be used for tissue impedancesensing for depth control.

Electrodes could be 360° annular bands or segmented circumferentially toallow determination of directionality. Independent electrode segmentsfor directionality may include for example two electrodes spacedcircumferentially apart and centered on 180° or up to 6 electrodescentered on 60° spacing around the circumference.

One or more electrodes may be used as a reference electrode for bloodpool impedance. Bipolar capabilities could be added by the addition of arelatively large surface area grounding electrode. Surface area shouldbe at least about 15× or 20× the area of the ablation electrode, and canbe located on a proximal sidewall of the needle, dilator or sheath,anywhere along the length such as from 100 mm proximally of the distaltip or more. The grounding electrode needs exposure to the blood pool,anywhere along the vasculature.

The grounding electrode(s) may alternatively be on the surface of thedilator or sheath, and configured for being in electrical communicationwith the hub. For example, the needle could have a separate proximalelectrode that is in physical, electrical contact with an electricallyconductive surface on the ID of the dilator and/or sheath. The sheathand/or dilator are the contact points to the blood pool. Alternatively,the dilator or sheath can be provided with an electrical conductor (wireor conductive polymer) to place the electrode in communication with thehub.

An electrode on the sheath can conveniently act as the bi-polar returnelectrode as it is continuously in contact with the blood pool. Thesheath electrode or any other of the electrodes disclosed herein canalso be used to facilitate imaging technologies such as the Kodex EPDimaging and navigation system available from Koninklijke Philips N.V.Such systems measure changing electric field gradients induced onintracardiac electrodes to enable catheter localization and real-time 3Dcardiac mapping.

The distal tip of the needle can have specific geometry to aid inperformance. The needle can be tapered from the distal tip up to thearea where it leaves the dilator: dimensions from 0.050″ down to 0.020″.Diametral steps may be provided to facilitate tactile feedback tooperator as it passes through the septum, such as at about 0.005″increments. The needle preferably has super-elastic characteristics asit extends from the dilator: shape could be simple ‘C’ or a 90° bend.Needle may exhibit variable flexural rigidity options based onprotrusion from dilator to achieve a longer or shorter moment arm.Longer proximal needle shaft with heavier wall tubing, or solid ortubular body.

The distal tip can have features to prevent sliding motion on the fossa,such as surface projections or roughness—shark skin type geometry. Orelectrical features such as micropulses of high energy to ‘tack’ to thetissue.

The proximal end of the shaft may be stiffer than the distal end of theshaft. The wall thickness may vary from about 0.020″ down to about0.005″. The dilator may be tapered from a large diameter proximal enddown to the standard 0.045″ at distal end. The OD may be stepped tocreate different rigidity characteristics—same effect as tapering, justanother way to make the proximal end stiffer.

The flexural rigidity of the shaft may be within the range of from about0.015 Nm2 to about 0.0008 Nm2, and in some implementations between about0.010 Nm2 and 0.014 Nm2. The tip and or shaft can be solid or hollow.The shaft can have a constant outside diameter along its length, or canbe tapered from larger to smaller in the distal direction, or may beprovided with one or two or more stepped diameter transitions 20.

In a cannulated needle implementation the needle can be provided with noports, a single distal end port, a distal end port plus one or two orthree or more side ports, or one or two or three or more side ports witha closed distal end (no end port).

One or more optical sensors may be carried by the distal tip, tovisualize location on fossa ovalis and/or evaluate tissue type orcondition. Wiring for the optical sensors may be run proximally througha central lumen to an electrical connector carried by the hub 26

The RF generator is preferably self-contained and battery powered, whichprovides inherent patient safety through the use of independent 12-24vDC battery power versus connection to an AC power supply. The generatorcan deliver a high-speed duty cycle from about 0.5 ms to about 10 msswitching for control of output power. Programmable, digital logic forgeneration of 400-500 kHz RF ablation signal.

The generator is configured for impedance detection for control of poweroutput through control of voltage or duty cycle through high speedprogrammable logic on an embedded computer processor. The impedancedetection is also used for identifying contact with tissue and toconfirm penetration of the target tissue wall.

When the RF needle and generator are combined, the system enablesautomatic tissue detection by impedance change between blood poolcontact and tissue contact. When the electrode is within the rightatrium or left atrium a first impedance level can be detected. When theelectrode comes into contact with the fossa, a second, differentimpedance can be detected. The second impedance is greater than thefirst impedance. For example, the first impedance may be within therange of from about 100-200Ω, while the second impedance may be withinthe range of from about 500-1000Ω. The second impedance may be at leastabout 50% or 100% or 200% or more higher than the first impedance. Thesystem may further be configured to differentiate tissue types based ontissue impedance (e.g., scar tissue versus absence of scar tissue)

The system may be configured to automatically change a characteristicsuch as power level based upon impedance changes. This is relevant sincewith smaller surface area of the electrode tip, and high impedancecrossing can be accomplished with lower power.

The impedance measurement enables an automatic power shutoff featurebased upon penetration through septum which produces a measurableimpedance change. Audible, visual and/or tactile feedback may beprovided at milestone events such as when the electrode tip is placed incontact with tissue, and when the electrode tip 24 has penetratedthrough the fossa and enters the left atrium.

Multiple electrodes may be utilized for redundancy and additionalfeatures. A secondary electrode may be spaced proximally apart from thedistal tip and positioned in the in the right atrium or left atriumblood pool for reference. A secondary electrode may be used for depth ofpenetration detection, and/or larger diameter enlargement. A secondarylarge surface area electrode (e.g., greater than about 15× or 20× theburn electrode surface area) in the proximal shaft may be utilized forbipolar system. Alternatively, the access sheath or dilator may be usedas the return electrode.

Additional specifications of an exemplary generator useful to enable theseptal crossing by the use of an 400 kHz to 500 kHz RF signal mayinclude the following features.

Voltage output from 7.5 V to 400 V at 460 kHz under the control of theembedded controller. The output power can be controlled by either theoutput voltage or the duty cycle. Both the voltage and duty cycle arecontrolled by the embedded controller.

The generator is capable of delivering 50 watts from 40 ohms to 2000ohms.

The voltage is variable from 7.5 V to 4000 V in 256 steps.

The duty cycle is variable from off to full on in 256 steps.

The duty cycle period is settable in 4 steps 0.556 ms 4.44 ms 0.071seconds and 1.13 seconds

The generator has a 4×20 LCD display.

The output values are programed by menus by controls such as pushbuttons.

The time duration power and impedance are displayed during powerdelivery.

The ablation signal is created by programable logic.

Power for the generator is provided by a 22.2 volt 1350 mah LIPO batterypack.

The signal is generated crystal controlled digitally and converted tosine wave by a series resonate circuit.

The voltage is stepped up by 12× by a high frequency isolationtransformer with 8 kv isolation and the resultant signal is coupled tothe output by a second series resonate circuit.

Beginning with FIG. 2A there is illustrated a cannulated embodiment of atissue penetrating apparatus 102 in a transseptal crossing system of thetype having one or more distal ports as will be discussed. Apparatus 102comprises an elongate tubular body 104 having a distal region 106, and aproximal region 108. Distal region 106 is adapted to be inserted withinand along a lumen of a body of a patient, such as a patient'svasculature, and maneuverable therethrough to a desired locationproximate material, such as tissue, to be perforated.

The tubular body 104 may have at least one lumen extending from proximalregion 108 to distal region 106 such as lumen 208 shown in FIG. 2B.Tubular body 104 may be constructed of a biocompatible polymer materialjacket typically with a tubular or solid metal core that providesconductivity and column strength to apparatus 102. Examples of suitablematerials for the tubular portion of tubular body 104 are stainlesssteel or nitinol, with an insulating outer jacket 209 comprisingpolyetheretherketone (PEEK), nylon, polyimide or other polymers known inthe art. In the illustrated embodiment, the outer diameter along thetubular portion of tubular body 104 may step down at transition 20 todistal segment 107. In alternate embodiments, the outer diameter alongtubular body 104 remains substantially constant from proximal region 108to distal segment 107.

Distal region 106 may be provided with a preset curve duringmanufacturing, typically by exposing it to mechanical force or heatwhile it is fixed in a desired shape. In an alternate embodiment, theshape of distal region is modifiable by the operator during use. In thepresent embodiment, the distal region 106 comprises a curve portion 115.

Distal segment 107 may have a smaller outer diameter compared to theremainder of tubular body 104 so that dilation of a perforation islimited while the distal segment 107 is advanced through theperforation. Limiting dilation seeks to ensures that the perforationwill not cause hemodynamic instability once apparatus 102 is removed. Insome embodiments, the outer diameter of distal segment 107 may be nolarger than about 0.8 mm to about 1.0 mm. For example, the outerdiameter of distal segment 107 may be about 0.9 mm (about 0.035″).Similarly, in some embodiments, the outer diameter of tubular body 104may be no larger than about 0.040″ to about 0.060″. For example, theouter diameter of tubular body 104 may be about 0.050″ (1.282 mm).

Distal segment 107 terminates at functional tip region 110, whichcomprises an energy delivery component and optionally also functions asan impedance and/or ECG measuring device. Functional tip region 110comprises at least one energy delivery tip 112 made of a conductive andoptionally radiopaque material, such as stainless steel, tungsten,platinum, or another metal. Distal region 106 may contain at least oneopening 109 which is in fluid communication with main lumen 208 (FIG.2A) as described further below.

In the illustrated embodiment, proximal region 108 comprises a hub 114,to which are attached a catheter connector cable 116, and electricalconnector 118. An adapter 119 such as a Luer connector is attached tohub 114 as well, for placing external fluid sources or devices intocommunication with the central lumen 208.

Proximal region 108 may also have one or more depth markings 113 toindicate distances from functional tip region 110, or other importantlandmarks on apparatus 102. Hub 114 comprises a curve direction ororientation indicator 111 that is located on the same side of apparatus102 as the concave side of the curve 115 in order to indicate thedirection of curve 115. Orientation indicator 111 may comprise aprojection, etching, or other indicium that facilitates perception ofrotational orientation.

In the illustrated embodiment, adapter 119 is configured to releaseablycouple apparatus 102 to an external pressure transducer via externaltubing. External pressure transducer is coupled to a monitoring systemthat converts a pressure signal from external pressure transducer anddisplays pressure as a function of time. FIG. 3 is a longitudinal crosssection through the needle shown in FIG. 2A.

FIGS. 4-10 show different geometries for the distal electrode tip.Referring to FIGS. 4A-4B, the electrode tip 24 may be provided with aplurality such as at least about two or four or six and in theillustrated implementation seven distally facing apertures 109 incommunication with the central lumen 208. The electrode tip 24 may beprovided with a hemispherical distal surface, and a proximally extendingattachment flange 120. Attachment flange 120 may fit within centrallumen 208 as illustrated, or may be an annular flange that slip fitsover the outside or within an annular recess on the outside surface ofthe advance segment 22.

Referring to FIGS. 5A and 5B, the electrode tip 24 may be provided witha diameter is larger than the diameter of the advance segment 22, toincrease the electrode footprint. The apertures 109 may be on the distalsurface of the tip 24, or may be on a side wall as illustrated in FIG.5B. The electrode tip 24 may be integrally formed with, or bonded to theadvance segment 22.

Referring to FIG. 6A-6C, there is illustrated a trans septal crossingneedle having both a distal end port 109 and at least one side port 122on the side wall of a tubular body spaced proximally apart from thedistal end port 109. The distal end 110 may be integrally formed withthe tubular sidewall 22. Alternatively, end 110 may be attached to adistal end of the tubular sidewall 22 such as by welding, adhesive, orother technique know in the art. Alternatively, the endcap 110 may beslip fit over the outside of the tubular sidewall 22, such as within anannular recess, to provide a smooth exterior profile. A radiopaquemarker 211 such as an annular ring may be embedded within or positionedin an annular recess in the sidewall 22.

FIG. 7A-7C illustrate an alternative configuration in which the distalend port 109 is in the form of two perpendicular slots In communicationwith the central lumen 208, and which provide four tissue contactingsurfaces for delivering RF energy to the fossa.

FIGS. 8A and 8B illustrate a distal needle configuration in which theelectrode 24 includes an attachment flange 120, such as a proximallyextending annular side wall configured to slip fit over the outside ofan annular recess in the tubular body 22. A distal aperture 109 isprovided in communication with the central lumen 208, as well as anoptional one or more side aperture 122. A tubular outer insulatingjacket 209 may extend distally over the attachment flange 120, andterminate to expose a distal electrode surface 24. The electrode 24 mayinclude a rounded annular shoulder 27 and a substantially planertransverse distal surface 29 depending upon desired electricalcharacteristics. Alternatively, the distal surface of the electrode 24may comprise a hemispherical, constant radius curvature having at leastone aperture 109 preferably coaxial with a longitudinal central accessof the needle.

A modified tip configuration is shown in FIG. 8C. A hemispherical distalsurface 29 extends proximally to a maximum OD at a step down 211 inouter diameter. The step down 211 is also at the intersection of thehemispherical surface 29 and the proximally extending connector such asan annular attachment flange 120. The OD of the attachment flange 120 isapproximately equal to the OD of the needle tubular body 22. With theattachment flange 120 seated within the annular recess on the distal endof the tubular body 22, the adjacent tubular body and the attachmentflange 120 provide a uniform OD, over which the insulating jacket 209resides. Any difference between the OD of the adjacent tubular body 22and the OD of the attachment flange 120 is generally less than about0.002′ and preferably less than about 0.001″. The thickness of thesidewall of insulating jacket 209 is approximately equal to the radialstep in OD 211 (e.g., any difference is no more than about 0.001″. Thusthe overall needle has a smooth constant OD, extending proximally fromthe electrode tip 24 across the junction between the flange and thetubular body.

In one implementation the electrode tip 24 comprises a radiopaque andhighly conductive material, which may be welded to a stainless steeltubular body 22. Preferably the material of the tip will have anelectric conductivity of at least about 44 (10.E6 Siemens/m) and athermal conductivity of at least about 300 W/m.K. In one implementationthe electrode tip comprises gold.

The insulating jacket 209 may be a solution coated or electrostaticcoated material that is adhesively bonded to the steel tubing.Preferably, the insulating jacket 209 is tough, elastic and conformal.

Selected dimensions of one implementation of the configuration of FIG.8C appear below. The distal tip 24 and insulating jacket 209 have an ODof no more than about 0.040 inches and in one implementation the OD isabout 0.032 inches. The axial length of the tip 24 from the step down211 to the distal apex is within the range of from about 0.01 to about0.02 inches and in one implementation is about 0.015 inches. The wallthickness of the attachment flange 120 is generally within the range offrom about 0.002 inches to about 0.005 inches and in one implementationis about 0.003 inches. The depth of the annular recess on the proximalside of step down 211 is generally within the range of from about 0.002inches to about 0.005 inches and in one implementation is about 0.003inches. The wall thickness of the tubular body at the bottom of theannular recess is generally within the range of from about 0.002 inchesto about 0.005 inches and in one implementation is about 0.003 inches.The wall thickness of the insulation layer is generally within the rangeof from about 0.002 inches to about 0.005 inches and in oneimplementation is about 0.003 inches. The OD of the annular recess isgenerally within the range of from about 0.015 inches to about 0.024inches and in one implementation is about 0.019 inches. The ID of thecentral lumen is generally within the range of from about 0.008 inchesand about 0.016 inches and in one implementation is about 0.013 inches.

FIGS. 9A-9B illustrate a configuration in which the distal electrodetissue contacting surface is substantially planer, and a plurality ofapertures 109 are provided on the distal surface. A central aperture 111is coaxially aligned with the longitudinal axis of the needle. Aplurality of secondary apertures 113 are arranged concentrically aboutthe central aperture 111. At least two or four or six secondaryapertures 113 are provided. In the illustrated embodiment, eightaperture surround the central aperture 111. Aperture diameter, number,and density may be determined depending upon the desired clinicalperformance.

FIGS. 10A-10B illustrate an implementation in which both a distalaperture 109 and at least one side aperture 122 are provided incommunication with the central lumen 208. The distal electrode 24 may beintegrally formed with the sidewall of the tubular body 22, may be inthe form of a cap, slip fit over the distal end of the tubular body, ormay be joined at a butt joint to the distal end of the tubular body andsecured such as by welding.

Referring to FIG. 11 , there is illustrated a schematic cross-section ofa portion of the heart 80. The right atrium 86 is in communication withthe inferior vena cava 88 and the superior vena cava 90. The rightatrium 86 is separated from the left atrium 16 by the intraatrial septum18. The fossa ovalis 92 is located on the intraatrial septum 18. As seenin FIG. 11 , a large bore transseptal sheath 82 may have a dilator 84,both riding over the RF needle 12 and guidewire, all positioned withinthe right atrium 86.

The combination of the sheath 82 with the dilator 84 having the RFneedle and GW extending distally therefrom, is then drawn proximallyfrom the superior vena cava while a curved section of the sheath, aloneor in combination with a preset curve at the distal region of dilator 84and or needle 12, causes the tip of the needle 12-GW combination to“drag” along the wall of the right atrium 86 and the septum 18, byproximal traction until the tip pops onto the fossa ovalis 92, as shownin FIG. 12 .

After the tip of the needle 12-GW combination has been placed in thedesired location against the fossa ovalis 92, RF energy is applied viathe tip 24 of the needle 12 to pass through the septum into the LA.

One medical technique is to confirm the presence of the tip of thetransseptal needle 12 within the left atrium 16. Confirmation of suchlocation may be accomplished by monitoring the pressure sensed through atransseptal needle lumen to ensure that the measured pressure is withinthe expected range and has a waveform configuration typical of leftatrial pressure. Alternatively, proper position within the left atrium16 may be confirmed by analysis of oxygen saturation level of the blooddrawn through an available lumen; i.e., aspirating fully oxygenatedblood. Visualization through fluoroscopy alone, or in combination withthe use of dye, may also serve to confirm the presence of the tip of thetransseptal 12 and GW in the left atrium 16. As discussed above, apreferred technique for confirming location of the tip is by monitoringa change in impedance at an electrode such as an the side wall of theneedle or at the distal tip. 3D mapping by measuring changing electricalfield gradients may also be used. The use of multiple electrodes totrack tip location is discussed below.

FIGS. 14A through 14C illustrate the transseptal crossing systemincluding the RF needle 12 and electrode tip 24 in accordance with thepresent invention. RF needle 12 is illustrated as extending through acentral lumen of dilator 84 and beyond the distal end of the dilator 84.A tapered dilator tip 85 extends between the main body of dilator 84 anda distal aperture. Dilator 84 is illustrated as extending through andbeyond the tubular access sheath 82. Access sheath 82 has a plurality ofside ports 83 within about 2 cm or 1 cm or less from the distal end ofthe sheath 82. The inside diameter of the lumen extending throughdilator 84 may taper to a smaller ID at the distal tip, at which point aminimal tolerance between the OD of the RF needle 12 and the ID of thedilator 84 is achieved.

A sheath handle 83 is provided at the proximal end of sheath 82 andenables communication of a sheath lumen with a flush line 87 separatedfrom a flush port 89 by stopcock 91. A hemostasis valve (notillustrated) is carried within sheath handle 83.

A dilator handle 93 is provided at the proximal end of the dilator 84. Afirst interlocking structure on the dilator handle 93 is releasablyengageable with a complimentary second interlocking structure on thesheath handle 83 to enable releasable positive engagement between thedilator 84 and the sheath 82. Needle handle 26 is provided with anindicium 32 of directional orientation Of the preset curve as has beendiscussed. Needle handle 26 is additionally provided with a flush port95 in fluid communication with the needle 12. Needle handle 26 isadditionally provided with a cable 28 leading to an electrical connector30 for providing electrical communication between the needle 12 andcontrol system which includes the RF power generator. Cable 28 andconnector 30 may additionally include electrical conductors inelectrical communication with each of any additional electrodes that maybe carried by the RF needle 12, dilator 84 or sheath 82.

As has been described in connection with previous implementations, theRF needle preferably includes at least one transition 20 between alarger diameter proximal section and the distal electrode tip. FIG. 15Aschematically illustrates an elongate graduated transition in which thediameter is reduced over a length of at least about 5 millimeters andsome implementations at least about 10 mm or 15 mm. In theimplementation illustrated in FIG. 15B, a first stepped or taperedtransition 20A is provided, spaced apart from an optional second steppedor tapered transition 20B by at least about 2 mm or 4 mm but generallyless than about 10 mm. Second transition 20B is generally within therange of from about 8 mm to about 4 mm from the distal tip.

Preferably, at least one of the sheath 82, the dilator 84, and theneedle 12 are provided with a preset curve to facilitate crossing thefossa 92. The curve is configured to provide backup support against thewall of the inferior vena cava 88 so that distal advance of the dilatorand sheath access assembly will optimize force from the needle againstthe fossa. Referring to FIG. 13 , a greater contact or crossing forcewould be achieved between the needle and the fossa if the side wall ofthe sheath 82 were seated against the opposing wall of the inferior venacava 88. For this purpose, the access assembly may be provided withpreset curves such as those illustrated in FIGS. 16A through 16C.

Referring to FIGS. 16A and 16B, there is schematically illustrated aneedle 12 having an electrode tip 24. A force vector F illustrates aforce vector from the fossa. Preferably, the needle 12 is pre curvedwith a convex side 97 opposite the electrode tip 24, to help maintainthe electrode tip 24 in contact with the fossa.

A proximal handle segment 302 extends between a proximal handle 26 and atransition 306. In one implementation, the handle segment 302 may havean axial length within the range of from about 6 cm to about 14 cm andoften within the range of from about 8 cm to about 12 cm. A proximalcurved segment 303 may extend distally from the first transition 306 andbe preformed with a curve having a best fit radius within the range offrom about 75 cm to about 250 cm.

A distal segment 308 extends between a second transition 305 and thedistal tip 24. The distal segment 308 may have a length within the rangeof from about 3 cm to about 10 cm and often within the range of fromabout 4 cm to about 6 cm. The distal segment 308 is provided with atighter radius of curvature than proximal segment 303. The best fitradius of curve of the distal segment 308 in the illustratedimplementation is generally within the range of from about 5 cm to about10 cm.

The preformed curvature in four different examples is illustrated inFIGS. 16C and 16D. In each instance, the distal segment 308 has a radiuswithin the range of from about 6 cm to about 9 cm and in oneimplementation about 8 cm. Proximal segment 302 in one implementation issubstantially straight. In a second implementation the proximal segment302 has a curvature within the range of from about 230 cm to about 250cm and in one implementation about 240 cm. In another implementation,proximal segment 302 has a curvature within the range of from about 100cm to about 120 cm and in one implementation about 115 cm. In anotherimplementation proximal segment 302 has a curvature within the range offrom about 65 cm to about 85 cm and in one implementation about 76 cm.

FIG. 16D illustrates some specific examples of the needle 12, withdimensions in cm. The distal segment 308 has approximately the sameradius in each, labeled 7.6 cm but may be +/−10% or +/−15% from thatvalue depending upon desired clinical performance. The radii ranges forthe successive proximal curves 302. Each of the X axis and Y axisdimensions can also be varied by +/−10% or +/−15% from that valuedepending upon desired clinical performance.

Multi electrode implementations are illustrated in FIGS. 17A through18B. The crossing assembly is illustrated in FIG. 17A in an imagingconfiguration. The dilator 84 extends distally of the sheath 82 toexpose a first dilator electrode 320 spaced apart from the seconddilator electrode 322. A third dilator electrode may be provided on thedistal end of taper 85 or on the electrode tip 24 on needle 12. Anadditional electrode may be carried by the sheath 82, depending upon thedesired clinical performance. In a crossing configuration (FIG. 17 ) theneedle 12 extends distally beyond the dilator 84 between about 5 mm and10 mm.

Additional multi electrode implementations are illustrated in FIGS. 18Aand 18B. Referring to FIG. 18A, the dilator may additionally be providedwith a third dilator electrode 324, and optional 4th dilator electrode326 and an optional tip dilator electrode 328. The electrodes arepreferably evenly spaced apart in an axial direction. Space betweenelectrodes may be at least about 2 millimeters or 4 millimeters or 6millimeters and generally less than about 12 millimeters or 10millimeters. The electrodes may have a width in the axial directionwithin the range of from about 0.5 mm to about 2.5 mm.

Referring to FIG. 19 , there is schematically illustrated arepresentation of a depth sensing dilator system for dilating apenetration in a tissue plane. A tissue plain may be an atrial orventricular septum, a percutaneous vascular access site, or other tissueplain.

The system includes an elongate flexible body, having a proximal end anda distal end as has been previously discussed herein. A tapered dilatorsegment is provided on the body. At least a first electrode 328 and asecond electrode 326 are spaced axillary apart along the body. Thesystem further includes a processor 350, and an output 352. Theprocessor 350 is configured to send a first signal to the output whenthe first electrode reaches a predetermined relationship with the tissueplane, and to send a second signal to the output when the secondelectrode reaches the predetermined relationship with the tissue plane.The predetermined relationship may be when the electrode first contactsthe tissue plane, or when the electrode passes through the tissue planesuch as into the left atrium blood pool beyond the tissue plane.

The output 352 may comprise at least one of an audio output, a visualoutput or a tactile output and may be displayed on a graphical userinterface on a monitor and or expressed audibly with a constant orpulsed tone or buzzer. At least one electrode is carried on the tapereddilator segment. The first and second electrodes may be spaced axiallyapart on the tapered dilator segment. The system may further comprise athird and optionally a fourth or fifth or more electrodes spacedproximally of the second electrode. The first second and third andadditional electrodes may be approximately equally axially spaced apartas has been previously discussed.

The system further comprises any of the RF generators 354 previouslydiscussed, configured to deliver RF energy to at least one of the firstand second electrodes and to conduct impedance measurements. Theprocessor 350 may be configured to determine impedance at at least oneof the electrodes. The RF generator may be battery powered as has beenpreviously discussed here in.

What is claimed is:
 1. A transseptal crossing system, comprising: atransseptal crossing needle comprising: an elongate, flexible outertubular body, having a proximal end, a distal end and an electricallyconductive sidewall defining a central lumen; an inner tubular bodycomprising a distal tubular segment extending from the distal end of theouter tubular body; an insulation layer surrounding the electricallyconductive sidewall of the outer tubular body and a portion of thedistal tubular segment and leaving exposed a distal electrode tip,wherein the distal electrode tip is located on the distal tubularsegment and defines a distal end of the transseptal crossing needle; anend aperture extending distally from the central lumen of the outertubular body through the distal electrode tip; and a hub coupled to theproximal end of the outer tubular body, wherein an axial spacing betweenthe inner tubular body and the hub is fixed; and a battery powered RFgenerator; wherein the generator is configured to deliver RF energy tothe distal electrode tip and also to measure impedance at the distalelectrode tip to provide information about the location of the distalelectrode tip, and wherein the generator is configured to detect animpedance change between the distal electrode tip contacting blood pooland the distal electrode tip contacting cardiac tissue.
 2. A transseptalcrossing system as in claim 1, further comprising at least one side portthrough the distal tubular segment spaced proximally of the electrodetip.
 3. A transseptal crossing system as in claim 1, further comprisingat least one side electrode on the distal tubular segment spacedproximally of the electrode tip.
 4. A transseptal crossing system as inclaim 1, wherein an outside diameter of the distal tubular segment issmaller than an outer diameter of the outer tubular body.
 5. Atransseptal crossing system as in claim 2, wherein the distal electrodetip comprises a smooth, hemispherical surface.
 6. A transseptal crossingsystem as in claim 1, wherein the sidewall comprises a stainless steeltube.
 7. A transseptal crossing system as in claim 1, wherein thetubular body has an outside diameter of about 0.35 inches.
 8. Atransseptal crossing system as in claim 1, having sufficient structuralintegrity to guide a large bore catheter transvascularly through aseptal wall and into a left atrium of the heart.
 9. A transseptalcrossing system as in claim 1, which exhibits sufficient structuralintegrity to guide a large bore catheter transvascularly through aseptal wall and into a left atrial appendage of the heart.
 10. Atransseptal crossing system as in claim 1, comprising an annular recesson a distal end of the distal tubular segment.
 11. A transseptalcrossing system as in claim 10, wherein the electrode tip includes aproximally extending connector positioned in the recess.
 12. Atransseptal crossing system as in claim 11, wherein the connectorcomprises a proximally extending annular flange.
 13. A transseptalcrossing system as in claim 12, wherein the annular flange has a firstoutside diameter and an outside diameter of the distal tubular segmenton a proximal side of the annular recess is about equal to the firstoutside diameter.
 14. A transseptal crossing system as in claim 13,wherein the electrode tip has a second outside diameter that is greaterthan the first outside diameter.
 15. A transseptal crossing system as inclaim 12, wherein the thickness of the insulation layer is about equalto the difference between the first outside diameter and the secondoutside diameter.
 16. A transseptal crossing system as in claim 1,further comprising a dilator having a dilator central lumen forreceiving the needle.
 17. A transseptal crossing system as in claim 16,further comprising a sheath having a sheath central lumen for receivingthe dilator.
 18. A transseptal crossing system as in claim 17, furthercomprising a first electrode on a distal end of the dilator.
 19. Atransseptal crossing system as in claim 18, further comprising at leasta second electrode on the sheath, spaced axially apart from the firstelectrode.
 20. A transseptal crossing system as in claim 19, furthercomprising a processor configured to determine impedance at least at thefirst electrode.